In a wireless transceiver system, an ideal isotropic antenna transmits radio frequency signals uniformly in directions. However, a large amount of energy in the transmit signals is not received by a receive antenna, leading to a relatively small received signal power and a relatively large space transmission power loss. According to beamforming technologies, a directional antenna beam may be generated to resolve the problem. An active phased array transceiver system is one of the beamforming technologies. In an active phased array transceiver system shown in FIG. 1, antennas are arranged linearly at an equal distance (d) to form an array, phase differences between input radio frequency signals of adjacent antennas are all α (that is, a latency ΔT), and a beam angle θ is determined by the following formula:
      θ    =                  sin                  -          1                    ⁡              (                              α                          2              ⁢              π                                ⁢                      λ            d                          )              ,where λ is a wavelength of a carrier f0 of a transmit signal.
Each transmitter controls the radio frequency signal phase difference α by using an independently controlled phase shifter. A minimum phase shift degree of the phase shifter is a phase shift precision, and a minimum phase shift degree of the beam angle θ is a scan precision. It can be learned from the beam angle calculation formula that, when the phased array system has a specific phase shift precision, a larger d between adjacent antennas indicates a higher scan precision θ, and the higher scan precision indicates a larger transmission radius of a transmit signal. Therefore, the scan precision of the phase shifter can be increased by increasing the phase shift precision of the phase shifter, to effectively increase the transmission radius of the signal transmitted by the system, and reduce the antenna distance. It can be learned that, a high-precision phase shifter is a key device for implementing a miniaturized phased array transceiver system having a high scan precision.
However, the prior art has the following disadvantages. Existing frequently-used phase shifters mainly include a passive phase shifter that is based on a passive scaling network, an active phase shifter, and the like. The passive phase shifter has a relatively large circuit area because an element such as an on-chip integrated inductor is used, and is inapplicable to a miniature wireless communications device. Moreover, a phase shift precision needs to be increased, and this further increases complexity of the passive scaling network, thereby making it difficult to satisfy requirements for miniaturization and a high precision. A circuit of an existing active phase shifter is complex, which is unfavorable to increase a phase shift precision, and a noise signal is easily introduced during quadrant switching performed by using an radio frequency (RF) path serially-connected switch that is commonly used in the active phase shifter, and deteriorates a phase error and an amplitude error and increases an insertion loss. Although the active phase shifter has a calibration circuit, the phase shift precision is not significantly increased after calibration (for an active phase shifter with a 4-bit precision, the phase shift precision can be increased by only 1 bit after calibration). Therefore, it is necessary to provide a new phase shifter, to satisfy phase shift control requirements for a high phase shift precision, miniaturization, and a small phase error/amplitude error.